1. Field of the Invention
The present invention relates to variable resistance systems, and more particularly, to an automatically adjustable system that is useful in providing variable resistance in exercise equipment.
2. Related Art
It is known that, for maximum benefit, an athlete in training must push himself to his maximum strength limits. This is difficult to achieve with conventional weight training equipment such as a bench press machine or other general purpose or special purpose machines since generally the athlete has heretofore stopped exercising when he reaches his first point of momentary muscular failure (MMF). At that point, the athlete must either personally change the weight on the machine he is using, or a second person must change the weight for him so that the athlete can continue using the machine. This either unnecessarily interrupts the exercise, or requires the continual presence of a second, non-exercising partner. If the athlete were able to experience multiple MMF's during any one set of specific exercise, he would eventually reach his absolute fatigue point (AFP). However, with conventional exercise equipment, the AFP is extremely difficult or impossible to reach due to the drawbacks described above.
Consider the case of an athlete lifting 120 pounds while doing bench presses. In this exercise, direct resistance is placed upon pectoral major and anterior deltoids. Soon, for example after only ten complete repetitions, this athlete is no longer able to complete another repetition. As a direct result, he stops exercising, even though he would be able to continue exercising at a lower weight amount, and ultimately reach his AFP.
Weight stacks of conventional exercise machines generally include a number of identical weight plates, or optionally include some smaller weights of a second value at the top of a stack, or which can be manually connected to the weight stack. Changing the weight resistance automatically in such a system can be complicated and expensive. For example, one possible approach is to provide individual automatically actuable selector pins for each plate that can be chosen as needed to choose the desired weight for the stack at that point in the exercise. Alternatively, a movable pin or pins can travel along the weight stack to the desired position for selecting the proper resistance. An exercise machine described in coassigned U.S. patent application Ser. No. 10/688,251, the entire specification of which is hereby incorporated by reference, utilizes actuators to select vertically oriented weight plates by pressing a tang into a recess.